Explaining geoengineering to normal people

[Andrew Lockley]

I've been trying to answer some basic questions from a lay inquirer on Twitter. I thought I'd share some of the explanations I've used.

I'd really value comments, corrections, ideas and feedback

A

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1. The sky will look hazy white, like it's viewed through a jug of water with a teaspoon of milk in it
2. SRM is much more about controlling future temperature rises than winding back old ones (near term).
3. Although sulphur injections aren't physically ideal, the fact that they're nature-identical reduces the risks of unforeseen consequences
4. Nobody working in geoengineering seriously believes it's an alternative to mitigation

[Mick West]

Regarding #1 "The sky will look hazy white, like it's viewed through a jug of water with a teaspoon of milk in it "

There's a few issues with that. For one, the sky actually does look hazy white a lot of the time, and in a lot of directions - most notably horizontal, with there being more atmosphere in that direction, and also in the direction of the sun, as there's more light. 

With Twitter, I've found using annotated images is the best way of getting a point across. For example:

Then "a jug of water with a teaspoon of milk in it" has a HUGE range of possible transparencies with variants on jug size, and milk type. Ideally you'd have an illustration that accurately reflects the computed magnitude. Is it one of these?

Feel free to use any of these images. 

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[Ken Caldeira]

The sky will not look hazy white.

It did not look hazy white after Mt Pinatubo. It is whiter, but still blue.  Maybe "slightly hazy blue" would be more accurate.

[Mick West]

Perhaps a simulated before and during image might work. Here's one with barely perceptible whitening. Are there calculations of the actual magnitude of the change? Or measurements (or even, ideally comparative photos) from Pinatubo.

[Ken Caldeira]

We did calculations in the attached paper.

We struggled with how to illustrate the color change but came up with no adequate solution.

_______________
Ken Caldeira

Carnegie Institution for Science 

Dept of Global Ecology

260 Panama Street, Stanford, CA 94305 USA

+1 650 704 7212 kcal...@carnegiescience.edu
http://dge.stanford.edu/labs/caldeiralab  

https://twitter.com/KenCaldeira

My assistant is Dawn Ross <dr...@carnegiescience.edu>, with access to incoming emails.

[Doug MacMartin]

Ben calculated the resulting spectrum of diffuse light for a range or aerosol concentrations and sizes; see attached.  Also has a comparison with Pinatubo, and with urban aerosols.

 

We were originally planning on putting colour patches into the paper, but concluded that the resulting colour depends too strongly on the monitor on which it is viewed or the printer used; even a pdf printed on the exact same printer by two different computers winds up looking quite different.  Furthermore, perceived colour depends on context.  So fair to say that it will look whiter, and closer to what people in urban areas are already used to, but hard to come up with a picture that is actually realistic.

 

(And, of course, it also depends on how much geoengineering you do, whether it is 0.5 Wm^-2 or 4 Wm^-2)

 

Doug

 

Alan has a photo from Mauna Loa during Pinatubo.

[Fred Zimmerman]

Good science discussion of this issue, but I think the GE community doesn't sufficiently take on board that consciously accepting an alteration in the appearance of the sky is a GIANT SHOW-STOPPING ROADBLOCK that will inspire ferocious and unending opposition.

ᐧ

[Mick West]

I understand that color varies greatly by view context, lighting, and display device. But surely an A/B side-by-side comparison could accurately demonstrate the magnitude and general direction of the change?

[Andrew Lockley]

Another way of looking at this is to create a standard.

UK pint glasses are always the same shape and size. UK semi skimmed milk is always the same fat content.

So there must be an accurate amount of milk you can put in a pint glass of water that gives you the right colour when you look at the sky through it.

To keep it simple we might use a doubling of CO2 from pre industrial, using only sulphur.

So, physicists: How much milk in my pint?

A

[Ken Caldeira]

Here is an attempt:

The left square is 100% blue. The right square adds in 10% green and red to try to make something like blue with 10% added white. This is the most whitening that we got in any calculation.

Saying it would 'whiten' the skies is exercising a bit of poetic license.

_______________
Ken Caldeira

Carnegie Institution for Science 

Dept of Global Ecology

260 Panama Street, Stanford, CA 94305 USA

+1 650 704 7212 kcal...@carnegiescience.edu
http://dge.stanford.edu/labs/caldeiralab  

https://twitter.com/KenCaldeira

My assistant is Dawn Ross <dr...@carnegiescience.edu>, with access to incoming emails.

[Mick West]

Here's something similar done to a photo. The left is straight from the camera, the right is overlaid with a pure white rectangle, at 10% transparency. I've left in the photoshop panels so you can see the setup. 

[Robert Tulip]

Pinatubo turned the sky yellow in Australia, as seen at the horizon in this shot Pinatubo dust colours the twilight

				Pinatubo dust colours the twilight Pinatubo dust colours the twilight AAO image reference MISC 17.     « Previous || Next » Image and text © 1985-2002, Australian Astronomical Observatory, Photogr...
				View on ftp.aao.gov.au	Preview by Yahoo

Would a slight change of sky colour really be a worse political problem than the effects of global warming?

---

From: Ken Caldeira <kcal...@carnegiescience.edu>
To: Mick West <mi...@mickwest.com>
Cc: Andrew Lockley <andrew....@gmail.com>; geoengineering <geoengi...@googlegroups.com>
Sent: Thursday, 8 January 2015, 8:10

Subject: Re: [geo] Explaining geoengineering to normal people

The sky will not look hazy white.

It did not look hazy white after Mt Pinatubo. It is whiter, but still blue.  Maybe "slightly hazy blue" would be more accurate.

On Wed, Jan 7, 2015 at 1:08 PM, Mick West <mi...@mickwest.com> wrote:

Regarding #1 "The sky will look hazy white, like it's viewed through a jug of water with a teaspoon of milk in it "

There's a few issues with that. For one, the sky actually does look hazy white a lot of the time, and in a lot of directions - most notably horizontal, with there being more atmosphere in that direction, and also in the direction of the sun, as there's more light. 

With Twitter, I've found using annotated images is the best way of getting a point across. For example:

Then "a jug of water with a teaspoon of milk in it" has a HUGE range of possible transparencies with variants on jug size, and milk type. Ideally you'd have an illustration that accurately reflects the computed magnitude. Is it one of these?

Feel free to use any of these images. 

On Wed, Jan 7, 2015 at 12:07 PM, Andrew Lockley <andrew....@gmail.com> wrote:

I've been trying to answer some basic questions from a lay inquirer on Twitter. I thought I'd share some of the explanations I've used.

I'd really value comments, corrections, ideas and feedback

A

-------

1. The sky will look hazy white, like it's viewed through a jug of water with a teaspoon of milk in it
2. SRM is much more about controlling future temperature rises than winding back old ones (near term).
3. Although sulphur injections aren't physically ideal, the fact that they're nature-identical reduces the risks of unforeseen consequences
4. Nobody working in geoengineering seriously believes it's an alternative to mitigation

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[Alexey Ryaboshapko]

Dear All,
Recent years I interviewed many people asking the question: “Did years of 1991 and 1992 have any distinguished (specific) characteristic in the nature?”  No one could remember any whitening the sky. They were shocked to know that the stratosphere contained 20-30 Mt of sulfate aerosol that period.
Alexey Ryaboshapko


Среда, 7 января 2015, 18:55 -08:00 от Ken Caldeira <kcal...@carnegiescience.edu>:

Alexey Ryaboshapko

[Stephen Salter]

Andrew

Lay enquirers might also like to understand the differnces between stratospheric sulphur and marine cloud brightening.

Stephen

Emeritus Professor of Engineering Design. School of Engineering. University of Edinburgh. Mayfield Road. Edinburgh EH9 3JL. Scotland S.Sa...@ed.ac.uk Tel +44 (0)131 650 5704 Cell 07795 203 195 WWW.see.ed.ac.uk/~shs YouTube Jamie Taylor Power for Change

--

[olivermorton]

Also worth noting that this is not a necessary effect; particles with less forward scattering would reduce the effect, as i understand it, and in principle might do so a lot. Given this I'm not sure you can say ab initio that stratospheric geoengineering would alter sky appearance in any perceptible way at all.

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[olivermorton]

On 4, perhaps more accurate to say that they believe it *shouldn't be treated as* an alternative

[Andrew Lockley]

---------- Forwarded message ----------
From: Kravitz, Ben <Ben.K...@pnnl.gov>
Date: 12 January 2015 at 17:49
Subject: Re: [geo] Explaining geoengineering to normal people

To: Doug MacMartin <macm...@cds.caltech.edu>, "andrew....@gmail.com" <andrew....@gmail.com>, "mi...@mickwest.com" <mi...@mickwest.com>

Hi folks -

Sorry for not replying quickly – I've been on travel.  I don't know what's already been exchanged or approved to be posted to the google group, but here's my response to this exchange.  Please feel free to repost this to the google group if you like.

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I've attached our paper looking at sky whitening resulting from stratospheric aerosols.  I think the best way to describe the sky after sulfate aerosol geoengineering is that skies will look whiter and brighter, very similar to the way the sky appears in polluted areas (like big cities).  I really like Mick's response – I think he makes the point quite well.

Determining color change is actually quite tricky, because color is highly dependent upon perception.  So I don't think even an A/B side-by-side comparison can demonstrate the general direction of the color change.  In the supplemental material of our GRL paper (attached), I would invite you to look at Figures 3-6.  The only differences between these figures are changes in the color matching function and the whitepoint (illuminant).  But as you can see, they're vastly different, and I don't think any consistent pattern of change can be derived from these figures.

Also keep in mind that these figures could look different depending on the device you use to view them.  As Doug was saying, I remember that when we were writing this paper, I printed out the figures to look at them.  I sent Doug the PDF, and he printed out the figures as well on the exact same printer.  His printed document was really, really different from mine.  If you think all of this is frustrating in terms of finding simple statements, imagine how we felt when we were writing the paper. :-)

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While I'm at it, I might as well give my opinions on Andrew's other questions.

2. SRM is much more about controlling future temperature rises than winding back old ones (near term).

I'm not very good at predicting the future, so I think it's difficult to answer this question.  I personally don't know how SRM might be used in the future, if it is used at all.  I also don't even know if temperature would be the goal of geoengineering, or if there is only a single goal.  Although I appreciate the goal of coming up with simple statements, I worry that this one is too simple.

3. Although sulphur injections aren't physically ideal, the fact that they're nature-identical reduces the risks of unforeseen consequences 

In some respects this is true, and in some it's really not true.  For example, there are still gaping holes in our understanding of the microphysical processes that would govern eventual particle size from sulfate aerosol injection.  I'm not quite sure that a blanket statement about risk is the best thing to do here.

4. Nobody working in geoengineering seriously believes it's an alternative to mitigation

Outstanding point!  My only suggestion is that this should be first on your list.

-----

Best wishes,

Ben

______________________________________________________

Ben Kravitz

Postdoctoral Research Associate

Atmospheric Sciences and Global Change Division

Pacific Northwest National Laboratory

P.O. Box 999, MSIN K9-24

Richland, WA  99352

Tel:  (509) 372-6846  Fax:  (509) 375-6448

ben.k...@pnnl.gov

From: Doug MacMartin <macm...@cds.caltech.edu>
Date: Wednesday, January 7, 2015 at 2:45 PM
To: Ben Kravitz <Ben.K...@pnnl.gov>
Subject: FW: [geo] Explaining geoengineering to normal people

Not sure if you get the google group messages in real time, but you might answer this better than I or Ken can…